[Pharo-users] What are RBPattern* classes in the AST?

Hi, i was browsing the classes of the AST and i am curious about the RBPattern* classes. What are they used for? The RBPatternParser's comment says that it is used "to search and transform source code". After looking a bit in the senders and class refs, it seems it is used for refactorings and other stuff. But is that used at some point in code compilation? Steven.